[20210304]bbed的assign命令.txt

--//曾經寫過一篇bbed的assign命令，實際上使用它使得使用bbed變得更加簡單快捷，不用考慮大小頭問題，比modify修改更加方便快捷。
--//昨天偶然發現assign還可以不寫offset完成同樣的功能以及assign存在的一些弊端。我透過一個刪除記錄並恢復部分記錄來說明問題：

1.環境：
SCOTT@book> @ ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SCOTT@book> create table deptx as select * from dept;
Table created.

SCOTT@book> select rowid,deptx.* from deptx;
ROWID                  DEPTNO DNAME          LOC
------------------ ---------- -------------- -------------
AAAWHpAAEAAAAKrAAA         10 ACCOUNTING     NEW YORK
AAAWHpAAEAAAAKrAAB         20 RESEARCH       DALLAS
AAAWHpAAEAAAAKrAAC         30 SALES          CHICAGO
AAAWHpAAEAAAAKrAAD         40 OPERATIONS     BOSTON

SCOTT@book> @ rowid AAAWHpAAEAAAAKrAAA
    OBJECT       FILE      BLOCK        ROW ROWID_DBA            DBA                  TEXT
---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------
     90601          4        683          0 0x10002AB           4,683                alter system dump datafile 4 block 683 ;

SCOTT@book> delete deptx where deptno in (20,40);
2 rows deleted.

SCOTT@book> commit ;
Commit complete.

SCOTT@book> alter system checkpoint ;
System altered.

2.嘗試恢復:
--//刪除後表示從0x2c->0x3c，注意不包括出現行遷移的情況。

$ echo -e "set dba 4,683\nset offset 0\n$(seq 4 | xargs -IQ echo -e 'find /x 3c curr \nset offset +2')" | rlbbed
BBED: Release 2.0.0.0.0 - Limited Production on Thu Mar 4 09:29:29 2021
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
************* !!! For Oracle Internal Use only !!! ***************
BBED> set count 64
        COUNT           64
BBED> set width 160
        WIDTH           160
BBED>   DBA             0x010002ab (16777899 4,683)
BBED>   OFFSET          0
BBED> File: /mnt/ramdisk/book/users01.dbf (4)
Block: 683                                                  Offsets: 146 to 209                                               Dba:0x010002ab
------------------------------------------------------------------------------------------------------------------------------------------------
3c1f241f 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
<64 bytes per line>

BBED>   OFFSET          148

BBED> File: /mnt/ramdisk/book/users01.dbf (4)
Block: 683                                                  Offsets: 8096 to 8159                                               Dba:0x010002ab
------------------------------------------------------------------------------------------------------------------------------------------------
3c020302 c1290a4f 50455241 54494f4e 5306424f 53544f4e 2c000302 c11f0553 414c4553 07434849 4341474f 3c020302 c1150852 45534541 52434806 44414c4c

<64 bytes per line>

BBED>   OFFSET          8098

BBED> File: /mnt/ramdisk/book/users01.dbf (4)
Block: 683                                                  Offsets: 8140 to 8191                                               Dba:0x010002ab
------------------------------------------------------------------------------------------------------------------------------------------------
3c020302 c1150852 45534541 52434806 44414c4c 41532c00 0302c10b 0a414343 4f554e54 494e4708 4e455720 594f524b 03068098

<64 bytes per line>

BBED>   OFFSET          8142
BBED> BBED-00212: search string not found
BBED>   OFFSET          8144
--//可以發現刪除表示偏移在8096，8140。
--//正常執行如下：
assign dba 4,683 offset 8096＝0x2c
assign dba 4,683 offset 8140＝0x2c

--//可以去掉offset，執行如下，這是我不小心寫錯才發現可以這樣操作：
assign dba 4,683 8096=0x2c
assign dba 4,683 8140=0x2c

BBED> assign dba 4,683 8096=0x2c
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
ub1 rowdata[0]                              @8096     0x2c
--//你可以發現修改的位置還是offset 8096的位置。

BBED> x /rncc dba 4,683 offset 8096
rowdata[0]                                  @8096
----------
flag@8096: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8097: 0x02
cols@8098:    3
col    0[2] @8099: 40
col   1[10] @8102: OPERATIONS
col    2[6] @8113: BOSTON

BBED> sum apply dba 4,683
Check value for File 4, Block 683:
current = 0xe1d0, required = 0xe1d0

BBED> verify dba 4,683
DBVERIFY - Verification starting
FILE = /mnt/ramdisk/book/users01.dbf
BLOCK = 683

Block Checking: DBA = 16777899, Block Type = KTB-managed data block
data header at 0xf54e7c
kdbchk: the amount of space used is not equal to block size
        used=98 fsc=42 avsp=7946 dtl=8064
Block 683 failed with check code 6110

--//我僅僅恢復1條，理論將修改fsc，這樣比較麻煩。
--//dtl - used -fsc = avsp.
--//8064-98-42 = 7924

BBED> set dba 4,683
        DBA             0x010002ab (16777899 4,683)

BBED> p kdbh.kdbhavsp
sb2 kdbhavsp                                @134      7946
--//偏移在134. 佔2個位元組。

BBED> assign 134=7924;
sb2 kdbhavsp                                @134      7924

--//我還可以寫成：
BBED> assign 135=7925;
sb2 kdbhavsp                                @134      7925

--//bbed的assign會透過偏移計算正確的位置，對齊賦值。當然我並不建議這樣操作，最佳的方式應該執行如下：

BBED> assign kdbh.kdbhavsp=7924;
sb2 kdbhavsp                                @134      7924

BBED> sum apply dba 4,683
Check value for File 4, Block 683:
current = 0xe02e, required = 0xe02e

BBED> verify dba 4,683
DBVERIFY - Verification starting
FILE = /mnt/ramdisk/book/users01.dbf
BLOCK = 683

Block Checking: DBA = 16777899, Block Type = KTB-managed data block
data header at 0xf76e7c
kdbchk: space available on commit is incorrect
        tosp=7992 fsc=42 stb=2 avsp=7924
Block 683 failed with check code 6111

--//avsp+stb+fsc=tosp.
--//7924+2+42 = 7968
BBED> p kdbh.kdbhtosp
sb2 kdbhtosp                                @136      7992

BBED> assign 136=7968
sb2 kdbhtosp                                @136      7968

BBED> sum apply dba 4,683
Check value for File 4, Block 683:
current = 0xe036, required = 0xe036

BBED> verify dba 4,683
DBVERIFY - Verification starting
FILE = /mnt/ramdisk/book/users01.dbf
BLOCK = 683

3.驗證看看。
SCOTT@book> alter system flush buffer_cache ;
System altered.

SCOTT@book> select rowid,deptx.* from deptx;
ROWID                  DEPTNO DNAME          LOC
------------------ ---------- -------------- -------------
AAAWHpAAEAAAAKrAAA         10 ACCOUNTING     NEW YORK
AAAWHpAAEAAAAKrAAC         30 SALES          CHICAGO
AAAWHpAAEAAAAKrAAD         40 OPERATIONS     BOSTON
--//恢復正確。

4.繼續嘗試：
--//不過我發現assign也存在1個缺點
BBED> p dba 4,683 kcbh
struct kcbh, 20 bytes                       @0
   ub1 type_kcbh                            @0        0x06
   ub1 frmt_kcbh                            @1        0xa2
   ub1 spare1_kcbh                          @2        0x00
   ub1 spare2_kcbh                          @3        0x00
   ub4 rdba_kcbh                            @4        0x010002ab
   ub4 bas_kcbh                             @8        0x17689880
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   ub2 wrp_kcbh                             @12       0x0003
   ub1 seq_kcbh                             @14       0x03
   ub1 flg_kcbh                             @15       0x06 (KCBHFDLC, KCBHFCKV)
   ub2 chkval_kcbh                          @16       0xe036
   ub2 spare3_kcbh                          @18       0x0000

--//嘗試修改kcbh.bas_kcbh.
BBED> assign 8=0x77689880
ub4 bas_kcbh                                @8        0x77689880
--//0x77689880 = 2003343488

BBED> assign 8=2003343488
ub4 bas_kcbh                                @8        0x77689880
--//10,16 進位制一樣沒有問題。
--//但是這樣修改存在缺點：
BBED> assign 8=0x87689880
BBED-00206: out of range offset (87689880)
--//第1位不能大於0x8.
--//0x87689880 = 2271778944

BBED> assign 8=2271778944
BBED-00207: invalid offset specifier (2271778944)

BBED> assign 8=0xa7689880
BBED-00207: invalid offset specifier (a7689880)
--//0xa7689880 = 2808649856

BBED> assign 8=2808649856
BBED-00207: invalid offset specifier (2808649856)
--//注意兩個提示無一樣。
--//也就是assign無法修改4位元組內容時，第1位不能是大於0x8.

BBED> assign kcbh.bas_kcbh=0x87689880
BBED-00206: out of range offset (87689880)

BBED> assign kcbh.bas_kcbh=0xa7689880
BBED-00207: invalid offset specifier (a7689880)

--//如果你的修改遇到這樣的情況就比較麻煩了，感覺這個是bbed的bug。

BBED> assign kcbh.bas_kcbh=0x17689880
ub4 bas_kcbh                                @8        0x17689880

BBED> assign offset 8 = 0xa7
ub4 bas_kcbh                                @8        0x000000a7
--//你可以發現這個時候assign將偏移轉換為一個整體，只能使用modify修改，實際上modify一樣有這個問題存在。
--//注意modify修改要考慮大小頭問題。
--//我以前的測試：
BBED> modify /x 8affffff dba 101,1 offset 40
BBED-00209: invalid number (8affffff)
------------
--//還原：
BBED> assign kcbh.bas_kcbh=0x17689880
ub4 bas_kcbh                                @8        0x17689880

5.總結：
--//總之知道bbed assign與modify這些缺點，才能更好的利用這個工具。

[20210304]bbed的assign命令.txt

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